Schistosomiasis
In-Depth Report

In-Depth From A.D.A.M. General Health Precautions

More than 50 million people from industrialized nations travel to developing countries each year. Such trips can pose significant health hazards. Travelers who plan to visit developing or tropical countries, as well as those embarking on prolonged vacations or arduous treks should take a number of precautions.

When You Return

If you develop any symptoms of illness upon your return to the United States, be sure to contact your doctor immediately. Let your doctor know where you have been, in addition to what symptoms you are experiencing.

In-Depth From A.D.A.M. Traveler's Diarrhea

Traveler's diarrhea (TD) is the most common health problem a traveler encounters. It is almost always caused by ingesting certain organisms in contaminated food or water. Diarrhea can also be caused -- particularly in children -- by anxiety, stress, allergies, fatigue, and dietary changes.

Symptoms and Course

Diarrhea frequently occurs within the first week of travel, but may develop at any point, even after returning home. Traveler's diarrhea causes four or five loose or watery stools per day. Vomiting may also occur. It usually lasts 3 or 4 days, but about 14% of cases last longer. In rare cases, the diarrhea lasts more than 3 months. When TD lasts a long time, it can cause post-infectious irritable bowel syndrome. Traveler's diarrhea is rarely life threatening, although it can be severely debilitating, especially in children. Weakness, reduced urine output, lightheadedness, and mental changes require immediate medical attention, especially in children. Life-threatening symptoms include reduced levels of consciousness, seizures, and coma.

Risk by Country

High-risk destinations include most of the developing countries of Latin America, Africa, the Middle East, and Asia. The risk varies widely, however.

Intermediate-risk destinations include most Southern European countries and a few Caribbean islands.

Low-risk destinations include Canada, Northern Europe, Australia, New Zealand, the United States, and some Caribbean islands.

Infectious Causes

A number of infectious organisms, including bacteria, parasites, and viruses, can cause diarrhea in travelers. These organisms are most often transmitted through contaminated food and water. Bacteria and viruses cause diarrhea within a few hours and up to 3 days, while diarrhea from parasites can occur 7 - 14 days after exposure. In about 10 - 50% of cases, the cause is unknown.

The most common bacterial cause of traveler's diarrhea is Escherichia coli(E. coli). Certain strains of this organism are toxic to the intestines. E. coli accounts for 20 - 50% of TD cases. It is found in soil, water, and milk and occurs in major regions in the world, with the highest rates in Latin America and the lowest in Asia. Diarrhea caused by E.coli is generally explosive, non-bloody, and accompanied by nausea, vomiting, cramps, and fever.

Noroviruses, also called Norwalk-like viruses, are an increasingly common cause of traveler's diarrhea in countries such as Mexico and Guatemala, and on cruise ships. Recent studies of travel in these destinations rank noroviruses second to E. coli for causing diarrhea.

Shigella is the bacterial cause of dysentery, affecting 15% of travelers. It is common in countries experiencing natural disasters, socioeconomic upheaval, and during times when clean food and water are hard to find. Shigella causes bloody, mucus-laden diarrhea along with fever, cramps, and exhaustion.

Campylobacter is a very common food- and water-borne bacterial cause of diarrhea in certain regions, notably Thailand and Morocco, during the winter.

Giardia is a parasite found in contaminated water in every country in the world. It can cause chronic diarrhea lasting for several weeks, in addition to vague pain, weight loss, excessive burping, bloating, and fatigue.

Entamoeba histolytica is a parasite prevalent Mexico, India, Africa, and Central and South America. It produces small stools that contain blood and mucus. If the condition becomes chronic, it can resemble inflammatory bowel disease (IBD). It is important to distinguish the two, since corticosteroids used to treat IBD can have dangerous effects in people carrying the parasite.

Water Precautions

Drinking contaminated water is the most common cause of acquiring traveler's diarrhea. The following methods or products help reduce exposure to contaminated water.

Boiling water is the best method for eliminating infectious organisms. There is some debate about how long to boil, but bringing the water to a good boil for at least 1 minute generally renders it safe to drink. Travelers might consider buying an electric heating coil to boil and purify tap water. (A plug adapter or voltage converter may be needed).

Carbonated bottled water may be used for brushing teeth and drinking. Carbonation increases the acid in the water and kills bacteria. Plain bottled water may not be safe, since it can be taken from contaminated sources. Even ice cubes can carry infection.

Iodine tablets such as Polar Pure, Globaline, or Potable-Aqua purify water. Water may be purified by adding one iodine tablet to a quart of water 30 minutes before drinking it. Adding 50 mg of vitamin C will eliminate the iodine taste and color. Purifying is not effective against parasites such as Cyclospora and Cryptosporidium.

Small portable water filters remove parasites and clear murky water without leaving a chemical taste. They are particularly beneficial for pregnant women and people who cannot take iodine. Filtering does not prevent viruses from passing through. When purchasing a filter, the phrase "EPA Registration" should be printed on the label, indicating that the U.S. Environmental Protection Agency has guaranteed its effectiveness.

Newer portable water purification systems, such as SteriPEN, use ultraviolet light to disinfect water. These handheld devices can destroy bacteria, viruses, and protozoa, such as Giardia and cryptosporidium.

In all cases, do not swim in water that may be contaminated or contain parasites.

Food Precautions

Some important tips:

Seek restaurants with a reputation for safety. Even then, avoiding raw foods, as well as fresh fruits or vegetables that do not need to be peeled, is advised.

Heated food should be hot to the touch and eaten promptly.

Beware of sliced fruit that may have been washed in contaminated water.

Don't buy food from street vendors.

Peel all fresh fruits and vegetables yourself.

Vegetables may also be rinsed with diluted soapy water, soaked in a halide solution, and rinsed in purified water. (Certain fruits, such as strawberries, raspberries, and grapes should never be considered safe, even when washed.)

Avoid dairy products.

Avoid raw or undercooked meat and fish.

Avoid cold toppings and sauces -- even bottled sauces on tables. In one study, two-thirds of tabletop sauces in Mexico were contaminated. (Forty percent of sauces on tables in Houston, Texas, were also contaminated.)

Avoid tap water and ice cubes.

Avoid fruit juices, fresh salads, and open buffets.

Preventive Drugs

There is no vaccine against traveler's diarrhea. However, vaccination against cholera has been shown to offer some protection against TD in 25% of travelers.

The following drugs can reduce your chance of getting sick:

Pepto-Bismol. Taking two tablets of Pepto-Bismol four times a day before and during international travel can help prevent many cases of diarrhea. Pepto-Bismol should not be taken for more than 3 weeks. Both aspirin and Pepto-Bismol share the active ingredient salicylate, which can be harmful to children. Many medications interfere with salicylate, and people who are allergic to aspirin, pregnant women, and those with ulcers, other bleeding disorders, or gout, should not take Pepto-Bismol without consulting a doctor. Side effects of Pepto-Bismol include ringing in the ears and black stools and tongue.

Prophylactic Antibiotics. Prophylactic antibiotics are those used to prevent diarrhea while traveling. They work well, but there are many reasons that argue against their routine use. Taking prophylactic antibiotics can trigger adverse drug reactions, development of infections with resistant strains, and contribute to the global problem of bacterial resistance. Antibiotics are also NOT effective against parasites or viruses, but their use may give travelers an unwarranted sense of security. At this time, prophylactic antibiotics are not generally recommended unless the person is at increased risk for complications of TD. People at such risk include those with chronic bowel diseases, kidney disease, diabetes, or HIV.

Lactobacilli. Taking capsules that contain protective bacteria called lactobacilli (also called probiotics), may be helpful, although the Infectious Diseases Society of American believes that evidence is insufficient to recommend them. Some studies report that a genetically engineered strain called Lactobacillus rhamnosus strain GG may prevent and reduce severity of diarrhea. In fact, lactobacilli may be used for both prevention and treatment in children without any adverse effects. The capsules can be split open and put into beverages for small children.

Treatment for Diarrhea

Fluid Replacement. If diarrhea develops, the most important steps to take are preventing dehydration and replacing lost fluids, particularly in children. In severe cases, dehydration can be life threatening. Agitation may be an early symptom of dangerous dehydration. Listlessness and a weak pulse are symptoms of severe dehydration. Parents should seek medical help immediately if the child appears to be dehydrated.

Ideally, fluid replacement utilize solutions that contain the important minerals potassium, sodium, and calcium. The following are some suggestions:

A useful recipe for fluid replacement calls for two glasses of fluid: the first containing 8 oz. of fruit juice, 1/2 tsp. of honey or corn syrup, and a pinch of salt; the second filled with 8 oz. of purified or carbonated water and 1/4 tsp. of baking soda. The traveler should drink alternately from each glass until the thirst is quenched.

Parents with small children should bring commercial oral rehydration solutions such as Pedialyte, Lytren, Gastrolyte, or Ricelyte. Products containing rice flour work slightly faster than others. If the child finds the taste unpleasant, adding a half-teaspoon of Jell-O or Kool Aid to sweeten the solution may help, and does not appear to reduce its benefits.

Adding a soluble fiber supplement and eating as soon as possible helps the intestine absorb water, and is beneficial for children and adults.

Children with diarrhea should not drink apple juice, colas, or sports beverages, because they do not contain the proper balance of salts and sugar.

Helpful Foods. Foods that help slow diarrhea include rice, bananas, apples, and tea.

Adding milk (but not soy milk) to these foods may help many children. In fact, eating yogurt that contains active lactobacilli cultures may have positive benefits. (However, yogurt drinks in developing countries may carry a high risk for contamination.)

Bismuth subsalicylate (Pepto-Bismol). Pepto-Bismol can be used for treatment of mild diarrhea and nausea. Treatment generally consists of 1 fluid ounce or 2 tablets every 30 minutes for up to 8 doses in a 24-hour period. If diarrhea continues, treatment can be repeated for a second day.

Loperamide (Imodium) is the agent of choice, even when used in combination with antibiotics.

Diphenoxylate (Lomotil).

Opiates (such as paregoric, tincture of opium, and codeine). Opiates are often poorly tolerated, and can affect the central nervous system.

Antimotility drugs should be discontinued if symptoms persist beyond 48 hours. They should NOT be used at all in patients with high fever, if there is blood in the stool, or in children under age 2. Imodium is approved for children 2 years and up, but its use in children is controversial because of reports of severe side effects. Experts do not recommend it.

Note: Lomotil and Imodium work well for treating diarrhea, but are not effective for prevention. Lomotil may even increase the risk for diarrhea.

Antibiotics. Antibiotics are generally effective for treating traveler's diarrhea that develops in an 8-hour period, with three or more loose stools, and especially if associated with nausea, vomiting, abdominal cramps, fever, or blood in the stools. Because antibiotics are prescription drugs, travelers at risk should obtain them before they depart and should receive directions for self-treatment while abroad. Antibiotics should not be used for nausea and vomiting when diarrhea is not present. Although self-treatment is generally safe, a doctor should be sought for any child with diarrhea and for adult patients who develop fever or bloody diarrhea. (Antibiotics are generally not useful for diarrhea in developed nations, since such cases are likely to be caused by viruses.)

In general, patients take one tablet every 12 hours for 5 days. Fluoroquinolones are the preferred antibiotic, unless the person is traveling to SE Asia or India, where bacterial resistance to this class of drugs is high. In these cases, azithromycin (Zithromax) is preferred. Taking a single dose of an antibiotic such as ofloxacin (Floxin), plus an anti-motility drug (usually Imodium), often provides relief within 24 hours for many patients. Other antibiotics used for diarrhea include ciprofloxacin (Cipro), rifaximin (Xifaxan), and levofloxacin (Levaquin).

Parasites do not usually respond to standard antibiotics. Trimethoprim-sulfamethoxazole (Bactrim), for example, has fallen out of favor for routine use because of resistant bacteria, but it may be very effective against the severe diarrhea caused by the parasite Cyclospora. Metronidazole (Flagyl) is the standard drug for Giardia. Erythromycin and similar antibiotics may be useful for Cryptosporidium or Campylobacter. Nitazoxanide is another antibiotic showing promise for treating diarrhea caused by parasites. Antibiotics do not work for diarrhea caused by viruses.

In-Depth From A.D.A.M. Other Infectious Diseases

An estimated 15 - 45% of short-term travelers experience a health problem associated with their trip. This percentage is higher in travelers to developing countries.

A traveler can reach virtually any place in the world within 36 hours, which is less than the incubation period for most infectious diseases. The ease with which people see the world has dramatically increased the number of foreign travelers. Respiratory infections, such as influenza and colds, develop in 10 - 25% of travelers. Women traveling to the tropics are at high risk for urinary tract infections.

Even worse, doctors in Western countries are now seeing infectious diseases never before encountered in their regions. Travelers are at risk from infections transmitted among people, as well as those transmitted by insects (vector-borne diseases). Malaria, which is transmitted by mosquitoes, is the most widespread vector-borne disease, and infects 300 - 500 million people world wide annually. Between 10,000 and 30,000 of these cases occur in travelers. Anyone traveling to high-risk countries should take precautions.

A Word about Bird Flu

Avian influenza type A (also known as bird flu and avian flu) is a disease causing death in more than 50% of infected persons. The virus (H5N1) is common in birds, but often does not make them appear ill. As of December 16, 2008, 391 people had been infected with the bird flu in 15 countries. Of these, 247 people have died, according to the World Health Organization. No cases have been seen in the United States. Risk factors for infection include close contact with caged birds or poultry (chickens, ducks, and turkeys), eating undercooked poultry products, and contact with poultry feces. To date, there are no documented cases of transmission of bird flu from one human to another. If they avoid these risk factors, travelers to countries with documented cases of avian flu are considered at low risk for infection. There are no travel restrictions associated with avian influenza, and preventive antiviral medications are not recommended.

Common Vector-Borne Diseases

Disease

Countries of Infection

Severity and Symptoms

Treatment and Prevention

Malaria

Parasite transmitted by anopheles mosquitoes.

The world''s number one infection, and nearly entirely preventable. Found in every tropical or subtropical country in the world.

Initial symptoms are flu-like, with possible nausea and vomiting. The skin may appear yellow. Without prompt treatment, can be fatal. Typically develops 10 - 30 days following exposure. Symptoms can occur for up to a year or more. People who have been in malarial countries should report fever or other symptoms plus travel information to their doctor even months after they return.

Treatment:
Immediate treatment is important, but the appropriate treatment depends on the traveler''s destination. There is widespread resistance to standard anti-malaria drugs such as chloroquine or primaquine. Alternative drugs include quinine, atovaquone/proguanil (Malarone), doxycycline, mefloquine (Lariam), hydrochloroquine, or derivatives of artemisinin.

Prevention: Many parasites are resistant to chloroquine. Alternative drugs include atovaquone-proguanil, mefloquine, and doxycycline. Malarone causes fewer side effects than other drugs. Lariam should not be used by people with history of psychiatric disorders. Doxycycline can cause photosensitivity. Prevention should focus on minimizing exposure to mosquitoes and "mosquito-proofing" living and sleeping accommodations.

Yellow Fever

Arbovirus transmitted by mosquito.

Nearly all cases occur in African countries near the equator and in tropical parts of South America.

Initial symptoms are usually flu-like and include headache, fatigue, fever, nausea, vomiting, and constipation. Severe symptoms include jaundice and hemorrhagic fever. Fatal in 23% of cases with severe symptoms. People who recover are immune for life.

Treatment: No exact treatment regimen for symptoms.

Prevention:Vaccination recommended before traveling to endemic areas. Vaccinations required for entry into certain countries. Vaccine not usually recommended for pregnant women, infants, nursing mothers, immunocompromised patients, or patients with history of thymus gland disease.

Symptoms may include fever, chills, headache, fluid accumulation in hands and feet, sleepiness, lethargy, and convulsions. Without treatment, the sickness is fatal.

Treatment: Pentamidine and suramin for early stages. Rimantadine under investigation. Melarsoprol and eflornithine for second stage. Nifurtimox being tested.

Prevention: Flies are attracted to dark, contrasting colors. Flies are not affected by insect repellents.

Chagas'' disease (American Trypanosomiasis)

Parasite transmitted by infected Reduviid bugs.

South and Central America

In the acute stage, symptoms can include a skin lesion, fever, loss of appetite, lymph node swelling, spleen and liver enlargement, and inflammation of the walls of the heart. Symptoms that may occur years or decades later include dementia, weakening of the heart, dilation of digestive tract, weight loss.

Treatment: Benznidazole and nifurtimox are usually only effective in acute attacks. Benzimidazole is also used for recurrences. Antiparasitic treatment may be recommended.

Prevention: Avoid buildings made of mud, adobe, and thatch, which can harbor the reduviid bug.

Dengue

Virus transmitted by mosquitoes.

Can occur in any tropical or subtropical country. Greater risk in cities than in the country. In 2005, dengue was comparable to malaria in global distribution.

Most plagues are transmitted by handling infected animals. However, the Indian pneumonic plague is airborne. Human plague reported in recent years in Africa, South East Asia, parts of South American and the US. Recently been reported in India, Vietnam and Zambia. Risk generally in rural mountainous areas.

Prevention: Use insect repellents and avoid handling any animals. Adults traveling to countries with plague outbreak may consider preventive antibiotics. Children may take sulfonamides. Vaccine under investigation.

Schistosomiasis

Schistosoma parasitic worms live off a specific snail in fresh water contaminated with feces.

Lake swimming in sub-Saharan Africa is a particular hazard for schistosomiasis in travelers. Other countries: Brazil, Puerto Rico, St. Lucia, Egypt, Southern China, the Philippines, and Southeast Asia.

Treatment: Tetracycline and oral hydration salts usually effective within 48 hours. Consume as much purified water as possible.

Prevention: Risk to travelers is considered low, and the vaccines are not produced in the U.S. or required for international travel.

Typhoid Fever and Parathyroid Fever
(Enteric Fever)

Bacterial infection (salmonella typhi) in contaminated water or food. Can be spread by flies.

Can occur in any region where food or water is contaminated. Outbreaks common after natural disasters in poor countries. Tends to occur in urban areas.

Initial flu-like symptoms and low-grade fever that increases every day for a week or more. In the second stage, fever stabilizes at 103 - 104 Â°F. "Pea soup" diarrhea or constipation can develop. Untreated, disease can last up to 4 weeks and is fatal in 10% of patients. After symptoms end, the patient is still infectious.

Treatment: Antibiotics essential. Ciprofloxacin is antibiotic of choice. Fluid replacement and nutrition maintenance is critical. Even when symptoms have resolved, patients may be contagious until bacteria is eliminated.

Prevention: Vaccinations recommended for travelers visiting high-risk countries for more than four weeks. Drink bottled water. Take same precautions as for traveler''s diarrhea.

Hepatitis A

Viral infection transmitted in contaminated water or food.

Worldwide. Highest risk in developing nations, particularly where sanitation is poor and cholera and typhoid are prevalent.

Prevention: Wash hands after using the bathroom. Two vaccines are available as well as combination vaccine for hepatitis A and B. Vaccination recommended for travel to any nation where risk is intermediate or high. Immunity from vaccine may develop more slowly in elderly people. CDC recommends vaccination 4 weeks before travel. HepA vaccine is recommended for all children at age 1.

Hepatitis B

Viral infection transmitted through contaminated blood, or through sex or sharing needles with an infected person. Can be passed from cuts, scrapes, and other breaks in the skin.

Common in Southeast Asia, Africa, the Middle East, islands of the South and Western Pacific, the Amazon region of South America, and the Mediterranean.

Flu-like mild symptoms. Sometimes rash, aching in joints. Symptoms usually appear 4 - 24 weeks after exposure but can occur long after initial infection. Often no symptoms, but even patients with symptoms can remain chronically infected with the virus.

Treatment: Treatment of symptoms.

Prevention: Several vaccines are now available, including a combination vaccine (Twinrix) for hepatitis A and B. Vaccination recommended for all children and for travelers to developing countries.

Symptoms in small children can be mild and flu-like. More likely to be serious in older children and adults. Symptoms include severe fever, headache, stiff neck and back, deep muscle pain. Can lead to paralysis and can be fatal.

Treatment: Treatments only for symptoms.

Prevention: Universal immunization with vaccine required. All babies should receive vaccination as part of standard vaccine schedule, with booster at 4 -6 years of age. Booster needed for adults traveling to developing country. Inactivated polio vaccine (IPV) is used.

Meningococcal Disease

Bacterial infection in the fluid and membranes covering the brain and spinal cord. Spread through coughs, sneezes.

The so-called meningitis belt (countries extending across sub-Sahara Africa from Nigeria to Somalia).

Fever, chills, headache, stiff neck, rash caused by bleeding into the skin, and vomiting. Can also cause pneumonia and loss of limbs. Particularly dangerous for children.

Treatment: Early administration of antibiotics is essential.

Prevention: Vaccines for travelers in the meningitis belt and other areas with outbreaks. Vaccine now recommended as standard for all children 11-12 years of age and entering college freshmen living in dorms and not previously vaccinated.

Leptospirosis

Exposure to bacteria from the urine of animals by swimming or bathing in contaminated fresh water.

Tropical and subtropical countries pose highest risk.

High fever, severe headache, diarrhea, and eye inflammation. In severe cases, can develop internal bleeding and liver and kidney damage.

Prevention: BCG vaccine available for children in developing countries. Not routinely used for travelers. Consider screening children who return from developing countries. Isoniazid or other medications can prevent acute disease in people who are infected but not ill.

Rabies

Virus transmitted from exposure to saliva from an infected animal (even from licking). Dogs are main carriers but all mammals susceptible.

Treatment: Immunoglobulins after bites, vaccine if not previously vaccinated (previously vaccinated travelers only require booster vaccine, but no immunoglobulins). Clean the wound with soap and water, and iodine if possible, immediately after bite. If symptoms develop, supportive treatments only.

Prevention: Vaccine is available and recommended for travelers who intend to work with animals or are likely to come in contact with animals in countries where the rabies virus is common. Immunization does not eliminate the need for treatment after exposure to the virus, but it does shorten the course of the disease.

In-Depth From A.D.A.M. Travel Precautions

Vector-borne diseases are infections transmitted by insects that harbor parasites, viruses, or bacteria. Common vector-borne diseases include yellow fever and malaria, but there are many others in every country in the world.

The risk for malaria and other mosquito-born infections is highest when mosquitoes feed, between dusk and dawn.

Insect Repellents

DEET. Most insect repellents contain the chemical DEET (N,N-diethyl-meta-toluamide), which remains the gold standard of currently available mosquito and tick repellents. DEET has been used for more than 40 years and is safe for most children when used as directed. Comparison studies suggest that DEET preparations are the most effective insect repellents now available.

Concentrations range from 4 - 100%. The concentration determines the duration of protection. Experts recommend that most adults and children over 12 years old use preparations containing a DEET concentration of 20 - 35% (such as Ultrathon), which provides complete protection for an average of 5 hours. (Higher DEET concentrations may be necessary for adults who are in high-risk regions for prolonged periods.)

DEET products should never be used on infants younger than 2 months. According to the Environmental Protection Agency (EPA), DEET products can safely be used on all children age 2 months and older. The EPA recommends that parents check insect repellant product labels for age restrictions. If there is no age restriction listed, the product is safe for any age. The American Academy of Pediatrics recommends that children use concentrations of 10% or less; 30% DEET is the maximum concentration that should be used for children. In deciding what level of concentration is most appropriate, parents should consider the amount of time that children will be spending outside, and the risk of mosquito bites and mosquito-borne disease.

When applying DEET, the following precautions should be taken:

Do not use on the face, and apply only enough to cover exposed skin on other areas.

Do not apply too much and do not use under clothing.

Do not apply over any cuts, wounds, or irritated skin.

Parents or an adult should apply repellent to a child instead of letting the child apply it. They should first put DEET on their own hands and then apply it to the child. They should avoid putting DEET near the child's eyes and mouth, and also on the hands (since children frequently touch their faces).

Wash any treated skin after going back inside.

If using a spray, apply DEET outdoors -- never indoors.

Do not apply spray repellents directly on anyone's face.

Other Insect Repellent Products. In 2005, the U.S. Centers for Disease Control (CDC) added two new mosquito repellents to its list of recommended products: Picaridin and oil of lemon eucalyptus. Picaridin, also known as KBR 3023 or Bayrepel, is an ingredient that has been used for many years in repellents sold in Europe, Latin America, and Asia. A product containing 7% picaridin is now available in the United States. Picaridin can safely be applied to young children and is also safe for women who are pregnant or breastfeeding. According to the CDC, insect repellents containing DEET or picaridin work better than other products. In scientific tests, oil of lemon eucalyptus, also known as PMD, worked as well as low concentrations of DEET. However, oil of lemon eucalyptus is not recommended for children under the age of 3 years.

Use of Permethrin. Permethrin is an insect repellent used as a spray for clothing and bed nets, which can repel insects for weeks when applied correctly. Electric vaporizing mats containing permethrin may be very helpful. A permethrin solution is also available for soaking items, but should never be applied to the skin. Side effects from direct exposure may include mild burning, stinging, itching, and rash, but in general, permethrin is very safe and its use may even reduce child mortality rates from malaria. Travelers allergic to chrysanthemum flowers or who are allergic to head-lice scabicides should avoid using permethrin.

Other Preventive Measures against Vector-borne Diseases:

Wear trousers and long-sleeved shirts, particularly at dusk. One survey suggested that this measure may significantly reduce the incidence of mosquito-born disease.

Sleep only in screened areas.

Air-conditioning may reduce mosquito infiltration. Where air-conditioning is not available, fans may be helpful. Mosquitoes appear to be reluctant to fly in windy air.

Do not wear perfumes.

Minimize skin exposure after dusk.

Wash hair at least twice a week.

Burning citronella candles reduces the likelihood of bites. (Indeed, burning any candle helps to some extent, perhaps because the generation of carbon dioxide diverts mosquitoes toward the flame.) Smoke from burning certain plants, including ginger, beetlenut, and coconut husks, have also reduced mosquito infiltration, but the irritating and toxic effects on the eyes and lungs (such as the seen with the citrosa plant) may be considerable. To date, no evidence shows much benefit to burning plants but such methods are not harmful.

Motion Sickness

About a third of the population is susceptible to motion sickness, with varying degrees of severity. The cause of motion sickness is still unclear. Some evidence suggests that, in susceptible people, motion triggers signals that the brain interprets as being in conflict with the brain's memory of correct position. It transmits this message to other parts of the body, which respond with sweating, nausea, salivating, and other symptoms of motion sickness. Other theories suggest that motion sickness is triggered by the body's inability to control its own posture and movement.

More women than men experience motion sickness. Women appear to be at higher risk just before and during menstruation. Motion sickness may also trigger migraines, even in people who do not ordinarily have them. Alcohol intake increases the risk of vomiting. The following are some remedies tried for motion sickness:

Medications. Prescribed medications include scopolamine as a patch (Transderm Scop), which is worn behind the ear and releases the drug slowly. Scopolamine is the most effective drug for motion sickness.

Over-the-counter medications include dimenhydrinate (Dramamine), meclizine (Bonine), and cyclizine (Marezine). Dramamine appears to be the most rapidly effective, although in one study Marezine caused less drowsiness and was more effective at reducing nausea after 3 minutes. Cinnarizine (Stugeron) is used in Europe and appears to be effective, with few side effects. It is not available in the US. None of these medications are as effective as prescription drugs but may be helpful for 6 - 12 hours. To ensure the drug achieves its desired effect, take oral medications at least an hour before traveling.

Nearly all the medications used for motion sickness, both prescription and nonprescription, can cause drowsiness, mouth dryness, and blurred vision. Scopolamine can cause heart rhythm disturbances. In one comparison study the scopolamine patch and cinnarizine had the fewest adverse effects on functioning. Dimenhydrinate had the most.

Non-medicinal Treatments. Common recommendations include focusing on the horizon (not on nearby areas), and avoiding alcohol and strong odors. Non-medicinal or alternative remedies are widely used, but are of unproven benefit. Some methods that have been tried include:

Taking ginger root capsules (2,000 mg) or eating large amounts of ginger starting about 12 hours before traveling. (Clinical studies are inconsistent on ginger's benefits, with some reporting relief without side effects.)

Acupressure (wrist bands and self pressure). Acupressure for motion involves exerting pressure on the P6 pressure point -- the so-called nausea-relief point. Travelers can try pressing on the nausea-relief point, located two finger widths below the crease of the wrist on the palm-up side and between the two major tendons leading to the hand. Studies have been inconsistent on the benefits of wrist bands. Some studies have reported relief with a wristband (such as ReliefBand) that uses batteries. These batteries create a small electric charge at the acupressure point. The device may cause a rash, and people with pacemakers should not use it.

Cold packs. In one study, applying cold packs to the forehead reduced the stomach activity of motion sickness.

Eating small meals. Protein meals may be more effective in controlling stomach activity than carbohydrates.

Behavioral Techniques. Some studies have reported relief by using certain behavioral approaches such as controlled breathing (concentrating on breathing gently or deeply), or listening to music.

Issues Involving Air Travel

Effects on Circulation. Traveling by car, airplane, or train for more than four hours increases the risk for blood clots in the legs (deep vein thrombosis, also known as DVT) in anyone. Those at highest risk include people with cardiovascular disease or its risk factors, people who have had recent surgery, cancer patients, and those taking oral contraceptives. Studies now suggest that DVT is the cause of more deaths than previously believed, because symptoms typically occur days after travel. In order to keep circulation moving during international flights or on trains, travelers should drink plenty of fluids, avoid salt, wear slippers, wear clothing that fits loosely in the waist and legs, take frequent walks in the aisles, and lift their legs up and down several times an hour. Two 2003 studies suggested that special stocking that compress the calves and ankles (such as Kendall Travel Socks, Sigvaris Traveno) may significantly prevent swelling and possibly blood clots due to long flights, even in travelers at medium to low risk.

Respiratory Infections. Flight cabins have very low humidity, which not only increases the risk for dehydration and dry eyes, but it also increases the risk for triggering disease in the airways. Fliers with colds or allergies are especially susceptible. The first rule is to drink plenty of liquids. Taking a decongestant tablet or nasal spray (not one containing an antihistamine) 30 minutes before flight can help prevent sinus and ear infections.

Of greater concern are studies suggesting that the prolonged time (8 hours or more) spent in the confined space of an airplane, combined with the close proximity to passengers from around the world, may facilitate the spread of serious contagious diseases such as tuberculosis and SARS. The CDC and World Health Organization now have guidelines on when and how to determine the need for preventive treatments after possible exposure to infectious organisms. (Recirculated air, which is now common in new aircraft, does not increase the risk for respiratory infections.)

Preventing Jet Lag. Crossing time zones can throw off the body's natural rhythms, especially when travelers fly from west to east. But jet lag can be minimized. A few days before long flights, adjust sleeping and eating patterns:

When traveling west, travelers might avoid outdoor light after 6 p.m.

If traveling east, travelers might begin going to bed earlier a few days before the trip and avoid outdoor light until 10 a.m.

If possible, flights should be completed well ahead of an important event requiring concentration.

If crossing multiple time zones, the traveler should schedule overnight stopovers.

The traveler should drink plenty of fluids, but avoid alcohol and coffee, which increase fluid loss.

Melatonin, a natural hormone associated with light changes, may help people recover from jet lag. Some people report good results by taking it on the day of departure a half hour before the expected sleeping time in the arrival city. Travelers might also ask their doctors about short-acting benzodiazepines ("sleeping pills") such as lorazepam (Ativan); benzodiazepine-receptor agonists such as zolpidem (Ambien) or eszopiclone (Lunesta); alprazolam (Xanax); or temazepam (Restoril). Note that these drugs have been known to cause short-term forgetfulness and other side effects, and should be tried at home before traveling.

Cruise Ships

Reports of illnesses aboard cruise ships, particularly gastrointestinal problems from contaminated food, have alarmed many travelers. A sanitation program conducted by the U.S. Public Health Service should significantly cut the risk for such problems. Cruise ships are inspected twice a year and are then rated. The CDC provides ratings to the public for all ships sailing from U.S. ports. At this time the ratings are the only guide for a healthy cruise. Meanwhile, cruise-ship travelers should avoid eating eggs and shellfish to help protect against diarrhea.

Aside from sanitation, health problems in general are common on cruise ships. A study of one major cruise ship reported that nearly 30% of the passengers were treated for skin disorders and 26% for respiratory problems while on board. The highly contagious norovirus, brought on board by one passenger, can quickly spread throughout the ship. Flu outbreaks sometimes occur even in summer. Older people who have not been immunized the previous flu season should ask their doctor about flu vaccinations. They add no value for people who had been previously immunized.

Preventing Skin Disorders

An estimated 3 - 10% of travelers experience some skin problem related to their trip, particularly when traveling to tropical and subtropical areas.

Avoiding Exposure to Sunlight. Many developing countries are in the tropics, were sunlight is intense. Ultraviolet radiation from sunlight not only can cause sunburn, but excessive sunlight and heat can cause toxic skin reactions in susceptible individuals. Everyone should avoid episodes of excessive sun exposure, particularly during the hours of 10 a.m. to 4 p.m., when sunlight pours down 80% of its daily dose of damaging ultraviolet radiation. Reflective surfaces like water, sand, concrete, and white-painted areas should be avoided. Clouds and haze are not protective. High altitudes increase the risk for burning in shorter time, compared to sea level and lower altitudes. Sunscreens and sunblocks with an SPF of 15 or higher are important and should be used generously. However, they should not be relied on for complete protection. Wearing sun-protective clothing is equally important, and provides even better protection than sunscreens. Everyone, including children, should wear hats with wide brims.

Preventing Skin Infections. People who visit the tropics or developing regions are at risk for a number of skin disorders, including infections with fungi and other organisms. Cleanliness is essential. Bathing or showering is very beneficial, but if there are no facilities, simply washing with soap and water (even if cold) is still helpful. (Note: Taking multiple daily showers can remove protective oils and is not recommended.)

The skin should also be kept dry in order to prevent fungal infections, which thrive in damp, warm climates. Take special care to clean and keep dry certain skin areas where infections are most likely to occur. They include creases in the skin, the armpits, the groin, buttocks, and areas between the toes. Use talcum powder in these areas. Keep socks dry.

Precautions when Traveling to High Altitudes

Acute high altitude illness, or mountain sickness, can affect the brain (mountain sickness, cerebral edema), the lungs (pulmonary edema), or both. Studies suggest that about 25% of mountain climbers experienced symptoms at 7,000 - 9,000 feet, and 42% of them have symptoms at 10,000 feet. Rapid ascension to high altitude, such as arrival by airplane, increases the risk. In most cases the condition is mild. Severe lack of oxygen at high altitudes, however, can cause serious problems in some people.

Acute Mountain Sickness. This syndrome is defined as headache and at least one other relevant symptom when a person travels to about 8,000 feet. Other symptoms include upset stomach, dizziness, weakness, fatigue, and difficulty sleeping. It typically develops in the first 12 hours, and may resolve spontaneously if the traveler remains at the same altitude.

High Altitude Cerebral Edema (HACE). HACE is a life-threatening brain swelling and the severe endpoint of acute mountain sickness. Symptoms include altered consciousness, loss of coordination, difficulty concentrating, and lethargy. In extreme cases, it can lead to coma and death.

High Altitude Pulmonary Edema (HAPE). HAPE is the occurrence of fluid in the lungs, which in rare cases can be severe. In one study, about 75% of mountain climbers who ascended to 15,000 feet had some mild form of HAPE. Worse performance and a dry cough suggest the onset of HAPE. In extreme cases it can cause severe lung deterioration. (If it is going to develop at all, HAPE usually occurs in the first 2 days and rarely after 4 days at a given altitude.)

Luckily, symptoms of the more severe complications come on slowly, are easily recognized, and resolve when returning to a lower altitude.

Risk Factors for High Altitude Sickness. The risk for high altitude sickness is determined by certain characteristics: The rate at which a person ascends; the altitude reached; altitude during sleep; and individual physiology. People who live yearlong at low altitudes are much more likely to be ill at greater heights. Being physically stronger is not protective. Certain common conditions (heart disease, diabetes, hypertension, mild emphysema, and pregnancy) play no role in a person's risk for high altitude sickness. (Upper respiratory infections, however, do increase the risk for HAPE.)

Precautions against Mountain Sickness. Acclimatization by staying several days at increasingly higher altitudes is recommended. If you take high blood pressure medication, ask your doctor about increasing dosage if traveling to high altitudes. And anyone with a chronic medical condition should check with his or her doctor.

The following are some measures for preventing mountain sickness.

As a rule, ascend no more than 1,000 feet per day at altitudes of 8,000 feet and above. Drink 6 - 8 glasses of water or juice a day and avoid alcohol.

Stop climbing when experiencing any symptoms of acute mountain sickness. Descend if symptoms worsen. Also descend immediately if you have any symptoms of HACE or HAPE.

Supplementary oxygen may be required for people who show signs of these conditions.

People who are hiking to very high altitudes may consider an inflatable chamber (Gamow bag and others). Such devices enclose a person, and when pumped up they simulate air pressure found at low altitudes.

Medications Preventing and Managing Mountain Sickness. Some medications are available for prevention or treatment of acute mountain sickness.

Ibuprofen (Advil) may be sufficient to manage headache associated with acute mountain sickness.

Acetazolamide (Ak-Zol, Diamox) taken one day before, and continued during initial exposure to high altitude, can reduce symptoms of acute mountain sickness, improve exercise performance and sleep, and reduce muscle and body fat loss. It may be used to treat minor symptoms of acute mountain sickness, but if symptoms persist, the traveler should descend to a lower altitude.

Dexamethasone (Decadron Phosphate, Dexasone, Hexadrol Phosphate) is used to treat acute mountain sickness and cerebral edema (HACE). Dexamethasone is not recommended for prevention, however, because of potentially dangerous side effects.

Nifedipine (Adalat) is used to treat pulmonary edema (HAPE) and may be used for prevention in people who know they are at high risk for HAPE.

Preventive use of salmeterol (Serevent), a long-acting inhaled asthma drug known as a beta-adrenergic agonist, may reduce the risk for HAPE by over 50%.

Precautions for Divers

Travelers planning to descend rather than ascend must also take precautions. Individuals with the following conditions should not scuba dive:

Heart and lung diseases

Bleeding disorders

Chronic ear infections or sinus infections blocking the ears

Diabetes

Pregnancy

History of seizures

History of migraine headaches

Diving, in fact, is becoming known as a cause of many types of headaches, and anyone with a history of chronic or frequent headaches should discuss these issues with a health professional familiar with this sport.

Avoiding Air Embolism. Air embolisms are bubbles that obstruct blood vessels and can occur in divers who hold their breath while swimming up to the surface. They can be life threatening and cause long-term neurologic impairment, including memory lapses, impaired thinking, and emotional disorders. Even tiny bubbles may do some harm over time. One study found that in amateur divers who dive frequently, tiny bubbles appeared to increase the risk for small brain lesions and degenerating spinal disks.

To eliminate these bubbles, experts recommend that you:

Ascend no faster than 30 feet per minute

Remain 15 feet below the surface for 3 - 5 minutes before surfacing

Avoid air travel for 24 hours after diving.

Drowning. The other major cause of scuba diving deaths is drowning in underwater caves due to improper training and poor equipment.

In-Depth From A.D.A.M. Traveling With Health Problems or While Pregnant

Diabetes

People with diabetes who do not require insulin injections do very well during international travel, provided they monitor diet and exercise. Insulin-dependent patients should remember that if they are traveling eastward the first day is shortened, and they will need less insulin. Westward travel means a longer day, thus will require additional insulin. Patients who travel by aircraft and need to carry syringes or needles now require medical documents.

Heart and Lung Diseases

People with any serious medical conditions should check with their doctor before travel. Of note, cabin pressure in aircraft is typically equal to about 5,000 - 8,000 feet above sea level. This can produce a 4% reduction of oxygen in the blood, which can affect patients with heart or lung problems.

Recommendations for Patients with Heart Risks. One study reported that over half the deaths that occurred in overseas travelers were due to heart disease. Generally, the following recommendations may be useful for travelers with a history of heart disease. Individual conditions vary, however, and any patient with heart disease, particularly a history of heart attack, should check with a doctor before traveling.

If you have had an uncomplicated heart attack, wait 4 - 6 weeks before traveling. A 2-week wait is recommended after uncomplicated bypass surgery. There are no restrictions after angioplasty, assuming you are not experiencing chest pain.

Implanted pacemakers and cardiac defibrillators can trigger metal detectors, so patients should have a card proving they have an implanted device and ask to be hand checked. Pacemaker patients should also carry an EKG taken with and without pacemaker activation. Defibrillators are found on board many commercial airlines. Patients should check to see if the airline trains their flight attendants on their use (rather than rely on traveling doctors, who may or may not be on board).

Patients with a history or risk of heart disease might be advised to wear elastic compression stockings and take low-dose aspirin before long trips to prevent blood clots. They should also take ordinary precautions, including drinking plenty of fluids, taking frequent walks, and performing leg-lifts several times an hour.

Recommendations for Patients with Lung Disease. The following are some recommendations for patients with lung disease:

For reasons of fuel economy, jets now fly higher and cabins are pressurized with up to 25% less oxygen than in the past. Patients with lung problems should consult their doctors about whether air travel might worsen their condition.

People who require supplemental in-flight oxygen cannot supply their own and must make arrangements with the airline. This requires a prescription and the patient must call the air carrier at least 48 hours before the flight. Not all carriers supply in-flight oxygen and none supply oxygen on the ground. That must be arranged separately.

Pregnancy

Pregnancy alters a woman's immune system. Before traveling to any country with health risks, pregnant women should note the following:

Avoid live vaccines, unless you plan to visit an area endemic for yellow fever. If you are in your first trimester, you should not receive any vaccines at all.

Be sure you are immune to rubella (German measles) before taking a cruise. Outbreaks of rubella have been reported on cruise ships; this normally harmless disease can cause fetal damage if a pregnant woman contracts it.

Take strict precautions against mosquitoes if traveling to countries where malaria occurs. Malaria can be especially severe in pregnant women, and may result in stillbirths or miscarriages. Pregnant women should consider postponing travel to areas with malaria, if possible.

Use portable water filters instead of iodine tables for purifying water.

Concerning air travel, pregnant women should consider the following:

Avoid frequent air travel. Although the emissions during flight are generally considered safe, very slight exposure to radiation from cosmic rays occurs.

To avoid problems during air travel, carry a letter from the doctor indicating the baby's due date. Most airlines prohibit women who are 35 or more weeks pregnant from flying internationally.

Walk in the aisles during long flights to help prevent blood clots. Wear seat belts low around your hips in case of air turbulence.

Try to avoid travel altogether if you are expecting multiple births, you have a history of preeclampsia (pregnancy-induced hypertension), or you are at high risk for other conditions such as circulatory problems.

Radiation from airport security scanners is minimal. However, pregnant passengers may request a hand-wand search.

Centers for Disease Control and Prevention. Revised Recommendations of the Advisory Committee on Immunization Practices to Vaccinate All Persons Aged 11--18 Years with Meningococcal Conjugate Vaccine. Morbidity and Mortality Weekly Report. 2007:56(31);794-795.

Centers for Disease Control and Prevention. Notice to Readers: Recommendation from the Advisory Committee on Immunization Practices (ACIP) for Use of Quadrivalent Meningococcal Conjugate Vaccine (MCV4) in Children Aged 2 - 10 Years at Increased Risk for Invasive Meningococcal Disease. Morbidity and Mortality Weekly Report. 2007;56(48);1265-1266

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